The present invention provides an apparatus and method for retrofitting a hydraulic roll actuating mechanism in a screw down rolling mill. In accordance with the present invention, an exterior housing element of the frame of the screw down mill is replaced by a hydraulic cylinder adapted to use the housing mounts, and to be positioned over the vertical opening in the frame which originally accommodated the actuating screw member. A piston rod sleeve extending from the hydraulic cylinder and enclosing the piston rod is fitted within the original screw member opening and threadedly engaged with the existing screw nut for transmitting reaction forces to the frame.
The provision of hydraulic roll actuation is frequently desired in existing screw down rolling mills to eliminate the inefficiencies of the mechanical screw arrangement and to provide the control advantages associated with the fast response to hydraulic systems. Presently, the conversion of a screw down mill to hydraulic actuation is a time consuming and expensive process. For example, the known conversion techniques and apparatus typically necessitate a month of mill down time which results not only in the direct conversion expenses but also the loss of significant production time.
In the conversion of rolling mills, it is desirable to avoid alteration of the frame since this not only generates significant expenses but also tends to reduce the frame structure and the capacity of the mill. Accordingly, conversion procedures have heretofore favored techniques wherein the hydraulic system is essentially fitted within the mill window either above the top backup chock or below the bottom backup chock. The fitting of the hydraulic system within the mill window imposes severe design restraints upon the hydraulic unit and, in many instances, the desired hydraulic unit still cannot be fitted within the mill window without significant reworking of the mill frame or backup chocks.
When a mill is originally designed for hydraulic actuation, it is desirable to locate the hydraulic unit clear of the mill window as illustrated in U.S. Pat. Nos. 3,242,711 and 3,435,649. In original designs, the remote disposition of the hydraulic cylinder allows sufficient space for preferred cylinder designs and removes the cylinder from the unfavorable environment of the rolling process. In addition, the unobstructed positioning of the hydraulic cylinder facilitates subsequent maintenance and enables certain control advantages.